Our objectives in this study are threefold: 1. To determine the incidence of colon polyposis in the family at risk. This will be done by performing barium enemas, sigmoidoscopic and colonoscopic examinations on all family members above the age of 10 years. 2. To perform a multiphasic immunological evaluation of the entire family. This will include the following in vitro techniques: (a) HL-A typing, (b) mixed lymphocyte culture (MLC) reactivity, (c) cell-mediated lympholysis (CML), (d) lymphocyte reactivity to plant lectins, endotoxins, and PPD, (e) T and B cell enumeration, (f) quantitation of chemotactic lymphokine production and quantitation of monocyte chemotactic responsiveness, and (g) quantitation of serum immunoglobulin levels. In vivo studies (cutaneous reactivity to common microbial antigens and to dinitrochlorobenzene (DNCB)) will also be performed. 3. To evaluate the use of two immunodiagnostic methods: (a) serum carcinoembryonic antigen (CEA) measurement and (b) cutaneous reactivity to the recently described soluble skin reactive antigen prepared from fetal colon) in detecting familial polyposis and/or adenocarcinoma of the colon.